They would howl like wild beasts, foamed at the mouth, and gnawed the iron rim of their shields. According to belief, during these fits they were immune to steel and fire, and made great havoc in the ranks of the enemy.

When the fever abated they were weak and tame. Accounts can be found in the sagas. To "go berserk" was to "hamask", which translates as "change form", in this case, as with the sense "enter a state of wild fury".

Some scholars have interpreted those who could transform as a berserker was typically as "hamrammr" or "shapestrong" — literally able to shape-shift into a bear's form.

This has sometimes been interpreted as the band of men being "hamrammr", though there is no major consensus. This is called 'going berserk'.

In Norse mythology, the wild boar was an animal sacred to the Vanir. The boar-warriors fought at the lead of a battle formation known as Svinfylking "the boar's head" that was wedge-shaped, and two of their champions formed the rani "snout".

They have been described as the masters of disguise, and of escape with an intimate knowledge of the landscape. Berserkers appear prominently in a multitude of other sagas and poems , many of which describe berserkers as ravenous men who loot , plunder, and kill indiscriminately.

Later, by Christian interpreters, the berserker was viewed as a "heathen devil". I'll ask of the berserks, you tasters of blood, Those intrepid heroes, how are they treated, Those who wade out into battle?

Wolf-skinned they are called. In battle They bear bloody shields. Red with blood are their spears when they come to fight. They form a closed group.

The prince in his wisdom puts trust in such men Who hack through enemy shields. The "tasters of blood" in this passage are thought to be ravens, which feasted on the slain.

The Icelandic historian and poet Snorri Sturluson — wrote the following description of berserkers in his Ynglinga saga:. His Odin 's men rushed forwards without armour, were as mad as dogs or wolves, bit their shields, and were strong as bears or wild oxen, and killed people at a blow, but neither fire nor iron told upon them.

This was called Berserkergang. King Harald Fairhair's use of berserkers as " shock troops " broadened his sphere of influence. Emphasis has been placed on the frenzied nature of the berserkers, hence the modern sense of the word "berserk".

However, the sources describe several other characteristics that have been ignored or neglected by modern commentators.

Snorri's assertion that "neither fire nor iron told upon them" is reiterated time after time. The sources frequently state that neither edged weapons nor fire affected the berserks, although they were not immune to clubs or other blunt instruments.

These men asked Halfdan to attack Hardbeen and his champions man by man; and he not only promised to fight, but assured himself the victory with most confident words.

When Hardbeen heard this, a demoniacal frenzy suddenly took him; he furiously bit and devoured the edges of his shield; he kept gulping down fiery coals; he snatched live embers in his mouth and let them pass down into his entrails; he rushed through the perils of crackling fires; and at last, when he had raved through every sort of madness, he turned his sword with raging hand against the hearts of six of his champions.

It is doubtful whether this madness came from thirst for battle or natural ferocity. Then with the remaining band of his champions he attacked Halfdan, who crushed him with a hammer of wondrous size, so that he lost both victory and life; paying the penalty both to Halfdan, whom he had challenged, and to the kings whose offspring he had violently ravished Similarly, Hrolf Kraki 's champions refuse to retreat "from fire or iron".

Another frequent motif refers to berserkers blunting their enemy's blades with spells or a glance from their evil eyes. This appears as early as Beowulf where it is a characteristic attributed to Grendel.

Both the fire eating and the immunity to edged weapons are reminiscent of tricks popularly ascribed to fakirs.

By the 12th century, organised berserker war-bands had disappeared. The Lewis Chessmen , found on the Isle of Lewis Outer Hebrides , Scotland but thought to be of Norse manufacture, include berserkers depicted biting their shields.

Scholar Hilda Ellis-Davidson draws a parallel between berserkers and the mention by the Byzantine emperor Constantine VII CE — in his book De cerimoniis aulae byzantinae "Book of Ceremonies of the Byzantine court" of a " Gothic Dance" performed by members of his Varangian Guard Norse warriors in the service of the Byzantine Empire , who took part wearing animal skins and masks: The rage the berserker experienced was referred to as berserkergang "going berserk".

This condition has been described as follows:. This fury, which was called berserkergang, occurred not only in the heat of battle, but also during laborious work.